Code style
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1. Please use `fixed integers`, see `stdint.h`_. Why? This library is compatible to different boards which use different architectures (8bit vs 32bit). So unfixed `int` has different sizes on different environments and may cause unpredictable behaviour.

2. If possible: use advantages of `c++11`, e.g. `constexpr`.

3. Add documentation to **every** new function or parameter. Add documentation to most steps in your source code.